Preparation and characterization of cinnamon essential oil nanocapsules and comparison of volatile components and antibacterial ability of cinnamon essential oil before and after encapsulation

Abstract

In the present study, cinnamon essential oil (CEO)-nanocapsules (CEO-NPs) were obtained through nanoprecipitation method by using chitosan and whey protein isolate (WPI) as wall materials. Effects of preparation conditions on the encapsulation efficiency (EE) were examined. The morphology and structures of CEO-NPs were analyzed through scanning electron microscopy (SEM), dynamic light scattering, fourier transformation infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Differences in volatile constituents of CEO before and after embedding were analyzed by gas chromatography-mass spectrometry (GC-MS). Additionally, the antibacterial activity differences between CEO and CEO-NPs were evaluated by measuring the diameter of inhibition zone (DIZ) and minimum inhibitory concentration (MIC). Results indicate that CEO-NPs having a size of 195.17 ± 1.35 nm and EE of 91.74 ± 1.10% are obtained when the wall material concentrations, pH, mass ratio of oil to wall materials, and emulsifier agent are 0.5% (w/w), 5, 1:1.8, and gelatin, respectively. FTIR revealed the encapsulation of CEO into nanocapsules, and DSC demonstrated the enhanced thermal stability of CEO after embedding. The zeta potential of CEO-NPs was found to be −31.7 ± 1.27 mV. Furthermore, GC-MS displayed the encapsulation of more than 90% ingredients of CEO into nanocapsules, and no significant difference in the main volatile constituents of CEO before and after embedding was observed. The MIC and DIZ values indicated a slightly decreased but more long-lasting and strong antibacterial activity of CEO-NPs against Staphylococcus aureus, Escherichia coli, Pseudomonas fragi, and Shewanella putrefaciens (sh2) during the 10-day storage period. Consequently, CEO-NPs could be employed as a potential natural preservative in food industry.